Consumer packagings for liquid contents such as milk, juice or the like occur in a number of different versions. One of the better known, generally occurring packaging container types is manufactured from a flexible, pliable packaging material which contains layers of paper and thermoplastic and is fed to a packaging machine in linear form. After shaping the line packaging material into a a tubular form, the material is cross-sealed at regular intervals, whereby mainly pillow-shaped packaging containers provided with projecting sealing tabs are formed. The pillow-shaped packaging containers are converted to a mainly parallelepiped shape by the projecting sealing tabs being folded down and the mainly triangular, double-wall corner flaps occurring in the shaping being folded inwards and sealed to the outside of the packaging container. A packaging container of this type is thereby given an upper end wall which is mainly rectangular and has a fold-out corner flap at each short end. One corner flap is, like the adjacent part of the upper end wall, provided with a weakening and tear indicator line which makes it possible to tear off a part of the corner of the packaging container and thereby obtain a suitable pouring opening whose form and extent can vary as a result of the adaptation to the type of product for which the packaging container is intended.
When the packaging container is to be opened, the corner flap provided with the opening device is freed from its seal against the side wall of the packaging container and is folded upwards and flattened from the sides, so that the consumer can tear off the part intended for this purpose and, provide a pouring opening. In order to ensure at the pouring thereby out of the contents through the pouring opening that a corresponding volume of air can simultaneously flow into the packaging container, the tear indication is usually shaped with a longish rear end, which mainly runs onward to the central part of the upper end wall. If the consumer does not open the packaging container completely, i.e. stops the tearing of the openable part before the material has broken as far as the aforesaid central part of the end wall, a surge problem arises in the pouring out of the contents, since the air is completely or partly prevented from penetrating into the packaging container. The same problem can also arise with certain product types of more viscous consistency.
In order to eliminate the above problem it has been proposed that the packaging container should be provided at the rear end of the upper end wall with a separate air hole, which is opened in connection with the opening of the packaging's pouring opening. It is, however, difficult to provide any form of automatic opening of this air hole, which makes two separate opening maneuver necessary before the pouring out of the contents. This has in practice proved difficult to put into effect, and the problem of poor air intake and therewith the ensuing surge problem therefore remains to a certain extent.